spark plug black and wet
 

my combo :
1969 rebuilt 400ci, h-beam rod, hypereutectic piston, 062 heads home ported, rpm performer with 800 quadrajet (rebuilt with cliff ruggle book), stock distributor with crane xri, new accel 300 wire set, new distributor cap

my problem :
the car start, run great but there a sound like a misfire. i check the spark plug and the cyl n°1 spark plug is black and wet while the other are good.
the spark plug fire well outside the head.
check the compression and it's ok on all cylinder
coolant level is good

what can it be ?

Pull the valve cover and see what your #1 rocker arms are doing.

already done and the 2 rockers move up and down
don't timing them but seems to be good in height and duration
the pushrods seem to be straight

Hi,
Is the wetness oil or gasoline?
If oil, then you may have a case where the gaps on the rings have aligned and are letting crankcase oil into the cylinder or the valve stem seal is torn or leaking. If gas, then the plug may not be firing in the cylinder. Swap it with another plug from an adjacent cylinder and run the engine. Your carb could be dribbling gas due to leaks. The gas would head for the cylinder that is connected by the lowest passage in the intake manifold. That could cause a wet plug while the car is setting still. Try driving in in different directions and then check all the plugs.
If more than one is wet, then the gas is getting slung around while the car in in motion.
Hope this helps.
Mike

sorry , i forgot to say it's gazoline on the spark plug

Even though you mentioned the plug firing outside the head, I'd temporarily swap another plug wire in place and see what happens.

I agree; the fact that the plug is wet indicates it is not firing. Replace the plug and if the same situation persits, replace the spark plug wire.

George

i've already replace the spark plug and wire, 2 times with different brand but change nothing

Is it possible that it is in the distrib cap?

the cap is a new one from ACCEL.
i think i will put my old PERTRONIX instead of the new CRANE XRi, just to see ......

i have replace the CRANE XRi with my old PERTRONIX and......... it works really better.
i can hear and feel all 8 cylinder.
but the n°1 spark plug is still wet, only on one side and less than before.
it looks like oil, but there's no blue smoke on the exhaust
the piston head is black and wet too.
i'm still searching what happen
if you have some ideas, i listen to you

Did you replace the spark plug at the time of the swap. The plug might not be "cleaning up."

no, just clean it.
good idea; i will try another one
thanks

are you running a pvc line into the intake?? if you are running it into the intake runner in the front. you might be sucking a little oil into the intake from the pvc.

i run one PCV line but directly in the plenum of the performer RPM.
http://img241.imageshack.us/img241/3512/pcvvk9.th.jpg

but yes, very close to the #1 cyl
i will try to disconect the PCV line

i have try other spark plug with the same result.
now the #1 cylinder work (i can hear and feel it) but the spark plug is still wet and i think it's not gasoline (i've try to fire it just after remove it) but OIL.
there's no blue or black smoke at the exhaust, the oil level is correct.

but if it's not that what it can be :
head's cracked ? valve stem seal ? cylinder ring ?

it cant be the rings if the compression is good. if the bulid up on the plug is black but fluffly carbon than that cylinder is running rich and also telling me that it is running too cold to burn off the deposits. now if it is black but has a wetness to it and feels oil like then most likely it is oil ether getting into the cylinder by bad valve stem seals or piston rings that havent seated fully yet. Im curious how many miles are on this engine? it might help us figure this out.

it has about 1500 miles.
jut taking out the intake manifold, and found a lot of oil above the valve.
i've made turning the engine with the starter and see ome oil comming from the top of the valve.
i think i's a worn valve guide because the valve stem seal are new.